UF studying disease linked to sandflies

Published: Friday, November 16, 2012 at 7:25 p.m.

Last Modified: Friday, November 16, 2012 at 7:25 p.m.

University of Florida scientists are searching for clues about a disease that both animals and humans can get called Leishmania siamensis after a horse in Ocala was diagnosed with it in August 2011, marking the first documented case of a horse in the U.S. with the disease.

"It's certainly not anything we want people to panic over. It is here, and there's a lot we don't know," said Sarah Reuss, assistant professor of large animal medicine at the UF College of Veterinary Medicine.

Reuss published a study in the September issue of Emerging Infectious Diseases that raises questions about the prevalence of the disease in U.S. horses and how it spreads to humans.

The sandfly, found in warm climates such as the Middle East, Central America and the Caribbean, transmits the disease, which has been found mostly in dogs, horses and humans. The disease causes skin lesions and is treated with anti-fungal medications.

The Ocala horse, a 10-year-old Morgan mare, recovered after about six months with anti-fungal medications, although horses often self-cure, Reuss said. A more severe form of the disease has been reported in dogs and humans.

"It can get into the bone marrow, liver and spleen, and can unfortunately be fatal," Reuss said, adding that Leishmania siamensis is the second-leading cause of parasitic-induced death in humans, after malaria.

In the U.S., the disease has been reported in more than 3,000 people, mostly in the Dallas-Fort Worth area and in members of the military returning from Iraq and Afghanistan.

Christine Petersen, an associate professor of veterinary pathology at Iowa State University's College of Veterinary Medicine, said dogs can transmit the disease to their puppies in utero, but scientists haven't found that to be the case with other species. Petersen added that the infected dogs were foxhounds, whose bodies are frequently under stress.

Similarly, humans with compromised immune systems are most at risk of contracting the disease.

"It won't happen in a normal healthy adult. It's kids, or elderly or otherwise immunocompromised people who are at highest risk," Petersen said.

And pregnant horses, like the Ocala horse, appear to be more vulnerable to the disease because of changes in the immune system, scientists speculate. Still, scientists are stumped over why some horses get the disease and others don't. None of the other horses on the farm where the Ocala horse lived had any signs of the disease, Reuss said.

Sandflies, a fuzzy insect about a third of the size of mosquitoes, are the only known transmitters of the disease. Their bites don't hurt but can cause itching, and the signature sign of infection with Leishmania siamensis is a red, raised sore that gets bigger and then heals over into a scar.

Sandflies are relatively prevalent in Florida, as they like sandy, brushy areas. UF researchers now are trapping sandflies to understand how prevalent the disease is among the flies and how they transmit it.

"We want to understand how much we really need to worry about this, or if this is sort of like a one-shot deal," Reuss said.

Petersen added, "I think it's something we should keep an eye on, particularly where we have disease-borne vectors in Texas and Florida. People are probably not going to be out anyway when it's really hot and gross, but for our pets, it's a lot bigger problem. Still, it's not a bad idea to use repellent."

Sandflies, like mosquitoes, feed at dawn and in the evening.

Reuss added that one concern is that global warming could spawn a potentially larger population of sandflies in warmer climates such as Florida.

"We know that sandflies are going to spread in their domain … and bring the disease with them," she said.

<p>University of Florida scientists are searching for clues about a disease that both animals and humans can get called Leishmania siamensis after a horse in Ocala was diagnosed with it in August 2011, marking the first documented case of a horse in the U.S. with the disease.</p><p>"It's certainly not anything we want people to panic over. It is here, and there's a lot we don't know," said Sarah Reuss, assistant professor of large animal medicine at the UF College of Veterinary Medicine.</p><p>Reuss published a study in the September issue of Emerging Infectious Diseases that raises questions about the prevalence of the disease in U.S. horses and how it spreads to humans.</p><p>The sandfly, found in warm climates such as the Middle East, Central America and the Caribbean, transmits the disease, which has been found mostly in dogs, horses and humans. The disease causes skin lesions and is treated with anti-fungal medications.</p><p>The Ocala horse, a 10-year-old Morgan mare, recovered after about six months with anti-fungal medications, although horses often self-cure, Reuss said. A more severe form of the disease has been reported in dogs and humans.</p><p>"It can get into the bone marrow, liver and spleen, and can unfortunately be fatal," Reuss said, adding that Leishmania siamensis is the second-leading cause of parasitic-induced death in humans, after malaria.</p><p>In the U.S., the disease has been reported in more than 3,000 people, mostly in the Dallas-Fort Worth area and in members of the military returning from Iraq and Afghanistan.</p><p>Christine Petersen, an associate professor of veterinary pathology at Iowa State University's College of Veterinary Medicine, said dogs can transmit the disease to their puppies in utero, but scientists haven't found that to be the case with other species. Petersen added that the infected dogs were foxhounds, whose bodies are frequently under stress.</p><p>Similarly, humans with compromised immune systems are most at risk of contracting the disease.</p><p>"It won't happen in a normal healthy adult. It's kids, or elderly or otherwise immunocompromised people who are at highest risk," Petersen said.</p><p>And pregnant horses, like the Ocala horse, appear to be more vulnerable to the disease because of changes in the immune system, scientists speculate. Still, scientists are stumped over why some horses get the disease and others don't. None of the other horses on the farm where the Ocala horse lived had any signs of the disease, Reuss said.</p><p>Sandflies, a fuzzy insect about a third of the size of mosquitoes, are the only known transmitters of the disease. Their bites don't hurt but can cause itching, and the signature sign of infection with Leishmania siamensis is a red, raised sore that gets bigger and then heals over into a scar.</p><p>Sandflies are relatively prevalent in Florida, as they like sandy, brushy areas. UF researchers now are trapping sandflies to understand how prevalent the disease is among the flies and how they transmit it.</p><p>"We want to understand how much we really need to worry about this, or if this is sort of like a one-shot deal," Reuss said.</p><p>Petersen added, "I think it's something we should keep an eye on, particularly where we have disease-borne vectors in Texas and Florida. People are probably not going to be out anyway when it's really hot and gross, but for our pets, it's a lot bigger problem. Still, it's not a bad idea to use repellent."</p><p>Sandflies, like mosquitoes, feed at dawn and in the evening.</p><p>Reuss added that one concern is that global warming could spawn a potentially larger population of sandflies in warmer climates such as Florida.</p><p>"We know that sandflies are going to spread in their domain … and bring the disease with them," she said.</p><p><i>Contact Kristine Crane at 338-3119 or kristine.crane@gvillesun.com.</i></p>